The case is one of the biggest tests facing the agency, known by its Indonesian initials KPK, which says $170 million was believed to have been stolen from the budget for the procurement of electronic identity (ID) cards.
The agency has come under repeated criticism from the establishment as it fights to root out corruption in Southeast Asia's biggest economy.
An unidentified attacker threw acid at a senior KPK investigator handling the ID card case early on Tuesday, Jakarta police spokesman Argo Yuwono said.
The investigator, Novel Baswedan, was being treated in hospital and police were investigating whether the attack was related to his work.
The KPK declined to comment on the attack.
The agency has put two suspects in the case on trial and they have told a court that at least 37 politicians benefited from the theft of funds from the ID procurement budget, including speaker Setya Novanto.
Novanto, who is also the chairman of Indonesia's second-biggest political party, Golkar, was not immediately available for comment. He has not been charged and has previously denied wrongdoing.
A public relations official for the KPK, Ipi Maryati, said Novanto had been banned from travel so that "whenever his information is needed in the investigation of the case, he's not out of the country".
Golkar's secretary general, Idrus Marham, told Reuters the party and Novanto would respect the legal process and Novanto would cooperate with the KPK.
"We also believe in the principle of innocent until proven guilty," Marham said.
The accusations made against Novanto and others, set out by the KPK in an indictment, say that sums ranging from $5,000 to $5.5 million were divided up in a room in parliament to members of various parties, including the one backing President Joko Widodo.
The president's party has said previously it was investigating the accusation and would follow the legal process.
The scale of the alleged theft has created sensational headlines in Indonesia, a country where corruption is endemic.
Global anti-graft watchdog Transparency International found in a recent survey that Indonesians perceived parliament to be their most corrupt institution.
The speaker of Indonesia's parliament, Setya Novanto, waves before meeting with Indonesian President Joko Widodo at the Presidential Palace in Jakarta, Indonesia March 14, 2017
Indonesia's anti-corruption agency has banned the speaker of parliament from overseas travel for six months in connection with a graft case involving new national identity cards, an agency official said on Tuesday.
